DESCRIPTION (Adapted from the Abstract): In this competing renewal application the Investigator seeks five years of support to continue a research program examining neural mechanisms and pathways underlying food intake and body weight regulation. The long-term goal of the project is to develop a comprehensive functional neuroanatomy of energy homeostasis. For the immediate future, the research focuses on a series of structure/function analyses of the vagus nerve and its interactions with the enteric and sympathetic innervation of the gut. The goal of the proposed studies is the completion of a series of morphological and functional analyses that are characterizing the types, topographies, and functions of vagal projections linking the brain and the GI tract. The first specific aim is to complete the characterization of different vagal afferent projections to the gut. This aim includes finishing an inventory of the different types of afferent endings in the various segments of the GI tract and generating comprehensive topographic maps of the distribution of each of the different endings. A proposed series of functional experiments will determine what separate roles different afferent populations play in the physiology of energy balance. Additional experiments will determine the time course and principles underlying a recently discovered active reorganization of vagal processes after selective denervations. The second aim is to perform a parallel series of structure/ function experiments on the vagal preganglionic or efferent projections to the GI tract. The third aim is to delineate the brain stem representation of vagal outflow to the GI tract. Characterizing more fully the final common path within the CNS of the vagus will provide the needed foundation for a full understanding of the hierarchically organized, descending pathways within the brain that link the CNS controls of feeding with the nutrient generated signals arising from the gastrointestinal tract.